Cooling of electronic tubes



Oct 25, 1 6 I c. A. E. BEURTHERET 3,280,897

COOLING OF ELECTRONIC TUBES Filed Jan. 29, 1964 2 Sheets-Sheet 1 I INVENTOR I l yms flLPHO/VSE l 5/1/45 sfommgr,

BY AA M ATTORNEYS Oct. 25, 1966 c. A. E. BEURTHERET 3,280,897

COOLING OF ELECTRONIC TUBES 2 Sheets-Sheet 2 Filed Jan. 29, 1964 INVENTOR C/l/QELAS flAPI/OMSE BY gwm.

ATTORNEY5 Patented Oct. 25, 1966 3,280,897 COOLING OF ELECTRONIC TUBES Charles Alphonse Emile Beurtheret, Paris, France, as-

signor to Compagnie Francaise Thomson-Houston, Paris, France, a French body corporate Filed Jan. 29, 1964, Ser. No. 341,067 8 Claims. (Cl. 16547) This application is a continuation-in-part of application Serial No. 30,720 filed May 19, 1960 and now abandoned.

Certain types of power electron tubes require the artificial cooling of several distinct parts of the tube or associated elements. For very high powers, it is convenient to use a liquid under forced circulation.

This invention concerns electron tubes in which heat is dissipated in diflerent parts having distinct functions. As .an example, in a high power Klystron device, the main dissipation of heat is located at the collector, but many parts of the body must also be cooled. The power to be dissipated at the collector is, for example, twenty times more than the total dissipation in the parts of the body.

The power dissipated at the various points in the electron tubes being generally of difierent orders of magnitude, they are usually cooled by means of independent circulations of which the respective deliveries are suited to the capacities of evacuation.

For example, in the case of a high power velocity modulation tube as above referred to, the collector is cooled by a circulation of water of 100 litres per minute, while the body is cooled by a delivery of 3 to 4 litres per minute. The warm liquid emerging from the various cooling water channels cannot be used again until it has been cooled again.

A recent improvement consists in applying to the collector an external structure permitting the cooling by evaporation of a liquid of a structure such as described in French Patent Number 1,060,761 and its additions, Numbers 61,100, 62,369 and 63,837, or any other similar structure. The quantity of liquid vaporized is very small and in the case of water, 1 litre per minute suflices to dissipate 40 kw. It has been found suitable that the greater part of the collector to be immersed in the liquid by enclosing the collector in a boiler which is supplied at constant level by the liquid obtained by condensing the vapor in a closed circuit.

The control of this level, its maintenance within the acceptable limits and the servicing and supply of the electron tube to meet such essential conditions are usually assured by the use of auxiliary devices which have been described chiefly in the French patent, Number 1,061,610, and its additions, Numbers 61,177, 61,178 and 61,518, or by an autoregulator system for the level, such as that described in French patent, Number 1,124,914.

Also, according to the teachings of the prior art, it is known how to feed the boiler associated with an anode (to be cooled by vaporization of a liquid) by a constant level device in connection with a tank on which the level of liquid is maintained constant (Patent 2,969,957, FIG- URES 1 to 5) or by feeding a larger quantity of liquid through a pump, the level being fixed by an overflow pipe which evacuates the excess of liquid and maintains a constant level in the boiler (Patent 2,969,957, FIGURE 4).

According to the present invention the boiler is fed at a constant rate and the excess of liquid is evacuated in a mixture with the steam. In the simplest form which the invention may take, the boiler must be wide and high enough in order to avoid a lack of water after a strong pulse of dissipated power. In this connection it is to be noted that if one volume of water is vaporized under atmospheric pressure, it makes 1700 volumes of vapor. If this escaping vapor takes away only 1/ 100 of its volume of unvaporized liquid, the rate of flow of liquid necessary to maintain the desired level is instead of 1. Consequently, it is an important auxiliary feature of this invention, to use adequate means to separate steam from liquid.

The present invention, which applies particularly to electron tubes having a part to be cooled, such as a collector situated at the upper part of the apparatus and which is at earth potential, consists in using, for the supply of the boiler containing the said part, the liquid from the circulation system cooling the body of the tube. The delivery of liquid being supposed to be greater than the maximum requirement of the boiler, this device permits elimination of all auxiliary apparatus for resupply at constant level. It is possible to fix the level at the desired height by providing for a simple over-flow of the liquid, the vapor being evacuated either upward or downward as has been taught in the patent above referred to and their addition patents.

In order better to understand the technical characteristics and the advantages of the invention, some embodiment thereof will now be described with reference to the accompanying drawings, on which:

FIGURES 1 and .2 represent schematically two variations of putting the invention into practice, more particularly concerning velocity modulation tubes or travelingwave tubes;

FIGURE 3 concerns certain details with a view to improving, within the idea of the invention, the separation of the liquid and the vapor; showing also an example of a safety device; and

FIGURE 4 shows an electrical circuit for the'purpose of controlling the tube in accordance with the level of the liquid in the boiler.

For reasons of ease in operation, it is convenient to direct the inlet channels for the liquid upwardly, and the simplest form of application of the invention is presented schematically as shown in FIGURE 1, in the case of a movement of vapor upwardly, and in FIGURE 2, in the case of a movement of vapor downwardly. In these figures, at 1 is shown the body of a tube of the Klystron type, for example, with the collector 2 directed upwardly. A channel 3 of small section receives the liquid under pressure which liquid coo ls various elements of the body 1. The two tube parts have only negligible thermal intercommunication and are provided with'sep; arate heat exchange structures. A connecting channel 4 links the warm water outlet to the base of the boiler 5 in which the level of the liquid is limited by an overflow channel 8 evacuating the liquid downwardly, while the vapor escapes upwardly 'by the channel 7 of which the larger section is adapted to the greater delivery of vapor. The heat exchange structure 5 on the part 2 is provided on that part since the collector 2 has the greatest heat dissipation. Boiler 5 thus surrounds the collector 2. The heat exchange structure with which the body 1 or the tube is equipped (e.g. chamber or coil) cools said body and is distinct and separate from the boiler 5 and the respective heat exchange structures are connected by channel 4. The channel 4 supplies the boiler 5 with the liquid which has already been heated in that it has served to cool the body 1.

FIGURE 2 differs only from FIGURE 1 in that the overflow channel 8 presents a section which is suificient to evacuate the excess of liquid and of vapor combined downwardly. The channel 7 of FIGURE 1 has been eliminated in FIGURE 2. But, in practice, the usual conditions of use of these tubes frequently prevents all downward evacuation, because of the presence of electrical elements associated with the tube and of thin screens designed to absorb harmful radiations from the tubes. Without the elements-for evacuation of liquid such as 8 in FIGURES 1 and 2, the arrangement contemplated by the invention would then present the inconvenience resulting from fiood ing the special collector structure in a mass of liquid above the desired level.

The consequences flowing from this excess of liquid above the desired level are particularly noticeable upon sudden variations of the rate of dissipation of heat. While at a low heat dissipation rate, the evacuation pipe system 7 essentially contains liquid emulsified with vapor up to the level of the culminating point '9. A sudden increase of dissipation, such as would be produced in the case of cessation of the high frequency electric oscillation, would have the effect of suddenly producing a considerable volume of vapor. This would act as a piston pushing the excess of liquid. Besides the risk of excess pressure which would slow the circulation of the liquid in the body of the tube, this phenomenon could force a large amount of water out of-the boiler. After this extensive evacuation the level of the liquid could be momentarily too low to assure, with certainty, the cooling of the collector.

It has been found that the use, without the teaching of the present invention, of a device for accelerating the internal circulation, similar to that described for operation at constant level in French patent Number 1,123,305, has the effect of assuring the maintenance in the boiler of a quantity of liquid sufiicient in all circumstances, and in spite of the sudden variations in routine operation. Such a device is represented in vertical cross section in FIG- URE 3. The boiler contains a cylindrical screen or shield 10 open at the two ends. A first set of fixed helicoidally oriented vanes 11 situated in the immediate vicinity of the upper part of the collector 2, makes the emulsion of liquid and vapor rotate rapidly. At the upper end of the screen or shield 10, the liquid is centrifuged in the direction of a second set of vanes 12, orientated along helices opposed to those vanes 11. The liquid is driven downwardly in the annular space 13, Where the longitudinal vanes 14 stop its movement of rotation. This method keeps the boiler 5 quite full of liquid and the vapor conducted towards the axis can only drive into the outlet channel 7 the quantity of liquid supplied in excess through the channel 4. Even if the de-- livery of liquid at the inlet of the boiler 5 is many times greater than the quantity vaporized, this form of the invention has the effect of diluting in the vapor the excess liquid, in such a way that the outlet tubes or channels 7 evacuate only the moist vapor.

On the contrary, when the power dissipated is zero or too small to produce an abundant vaporization, the excess liquid encumbersthe outlet tube or channel 7, as has been shown above. Although the presence of this liquid may not be inconvenient in the case of this last embodiment of the invention, it will be found advantageous to limit the static pressure which it imposes on the boiler in the case where the outlet tube or channel 7 presents great length. It is suflicient to provide (FIGURE 3) a drain 15 of small section at a suitable point of the pipe system 7, to limit the level attained by the liquid. After condensation of the vapor, the cooled liquid can be used again in closed circuit to supply the pipe system 3 and other auxiliary circulations (not shown) in the equipment associated with the tube. This circulation will be obtained generally by means of a pump of very low power. Moreover, the tube equipped in accordance with the invention is suitable in certain cases for a circulation of liquid by thermosyphon action.' It is suflicient if the condenser for the vapor is situated at an altitude sufiicient for the condensed liquid to present a static pressure equal to the loss of load imposed by the cooling circuit.

The safety of operation of the various embodiments of the invention requires the presence of liquid in the boiler up to the determined level, and to facilitate such safety the boiler has, preferably, a metal level-sensing probe 16 supported by an insulator 17 and connected to an external terminal 18 permitting the presence or absence of liquid at the desired level to be recorded by the variation of the electric-a1 conductivity between the terminal 18 and the boiler 5.

The terminal 18 is connected to one of the ends of the coil 19 of a very sensitive relay of which the other end is connected through a voltage source 21 to the boiler 5. The contacts 20 of the said relay are inserted in a circuit comprising the voltage source 21 and the coil '22 of a power relay. 'I'he contacts 23 of the latter relay are inserted in the supply line to a high voltage rectifier 25, connected at 24 to an alternating current supply, the terminals 26 of the saidrectifier providing the supply voltage for the electronic tube; When thelevel of liquid falls below the probe 16, the contacts 20 and 23 are successively opened and the supply voltage of the electronic tube is cut off, because due to a lack of liquid, the resistance between the probe 16 and the boiler increases and serves to shut down the operation of the electronic tube.

Klystrons, traveling-wave tubes and all similar tubes furnished with an apparatus in accordance with this invention, are new industrial products presenting characteristics of great advantage.

Thus, the present invention is particularly directed to the cooling of electronic tubes having two spatially distinct parts to be cooled which'have only negligible thermal intercom'munication between them, one of said parts having relatively low heat energy dissipation and the other of said parts having a relatively high energy dissipation. The desired cooling is achieved by firstly circulating the liquid over the part having a relatively low heat energy dissipation without attaining the point of ebullition of the liquid and then passing this same liquid over the part having a relatively high heat energy dissipation, where the liquid is allowed to boil so that cooling is effected by partial evaporation of the liquid at the surface of this latter part.

I'claim:

1. An arrangement for cooling an electronic tube having two spatially distinct parts to be cooled which have only negligible thermal intercommunicati-on between them, one of said par-ts having a relatively low heat energy dissipation and the other of said parts having a relatively high heat energy dissipation, comprising a cooling liquid jacket surrounding the first of said parts and a boiler surrounding the other of said parts and mean-s interconnecting said jacket and boiler for the flow of a cooling liquid from the jacket to the boiler, means for effecting a single circulation of cooling liquid successively through said jacket and boiler over the one and the other parts of said tube, said liquid circulation firstly cooling said one part having a relativelyl-ow heat energy dissipation in said jacket without-attaining ebullition and secondly cooling said other part having a relatively high heat energy dissipation by partial evaporation of the liquid in said boiler at the surface of said other part, and means for supplying liquid to said circulation system at least in a quantity equal to that which is vaporized during the cooling of said other part.

2. An arrangement as claimed in claim 1, including means arranged adjacent said other part to impart a centrifugal action to the mixture of liquid and vapor'to facilitate separation of the vapor from the liquid.

3. Aniarrangement as claimed in claim 2, in which the means for imparting centrifugal action comprises two sets of helical vanes orientated respectively in opposite directions.

4. An arrangement as claimed in claim 1, includin means for maintaining the liquid surrounding said other part at a desired level and for cutting off the power supply to said tube if the liquid falls'below said desired level.

5. An arrangement as claimed in claim 1, which constituted a closed-circuit system, and further including means for condensing the liquid vaporized during the cooling of said other part.

6. In combination, a high-power electron tube including a body part and a collector part, the collector part being disposed generally at one end of the body part and having a rate of heat dissipation many times higher than that of the body part in the operation of the tube, and a two-stage cooling system for said tube comprising a liquid cooling jacket surrounding the body part, a boiler surrounding the collector part, means interconnecting the jacket and boiler and means for circulating a common stream of cooling liquid serially first through the jacket and then through the boiler for first cooling the body part Without vaporization in said jacket and then cooling the collector part by partial vaporization in said boiler, said circulating means including means for discharging liquid and vapor from the boiler and means for supplying liquid to the jacket at a rate at least equal to the rate of vaporization in the boiler.

7. The combination defined in claim 6, including helical vane means arranged in said boiler adjacent said liquid and vapor discharging means for assisting in the separation of vapor from liquid.

8. The combination defined in claim 6, wherein said tube is arranged generally vertical with said body part at the base and said collector part at the top of the tube.

References Cited by the Examiner UNITED STATES PATENTS ROBERT A. OLEARY, Primary Examiner.

20 A. W. DAVIS, Assistant Examiner. 

6. IN COMBINATION, A HIGH-POWER ELECTRON TUBE INCLUDING A BODY PART AND A COLLECTOR PART, THE COLLECTOR PART BEING DISPOSED GENERALLY AT ONE END OF THE BODY PART AND HAVING A RATE OF HEAT DISSIPATION MANY TIMES HIGHER THAN THAT OF THE BODY PART IN THE OPERATION OF THE TUBE, AND A TWO-STAGE COOLING SYSTEM FOR SAID TUBE COMPRISING A LIQUID COOLING JACKET SURROUNDING THE BODY PART, A BOILER SURROUNDING THE COLLECTOR PART, MEANS INTERCONNECTING THE JACKET AND BOILER AND MEANS FOR CIRCULATING A COMMON STREAM OF COOLING LIQUID SERIALLY FIRST THROUGH THE JACKET AND THEN THROUGH THE BOILER FOR FIRST COOLING THE BODY PART WITHOUT VAPORIZATION IN SAID JACKET AND THEN COOLING THE COLLECTOR PART BY PARTIAL VAPORIZATION IN SAID BOILER, SAID CIRCULATING MEANS INCLUDING MEANS FOR DISCHARGING LIQUID AND VAPOR FROM THE BOILER AND MEANS FOR SUPPLYING LIQUID TO THE JACKET AT A RATE AT LEAST EQUAL TO THE RATE OF VAPORIZATION IN THE BOILER. 